A portion of the disclosure in this patent document contains material which is subject to copyright protection and to which a claim of copyright protection is made. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office patent files or records, but otherwise reserves all copyrights whatsoever.
Often in the use of a computer, it is desirable to input two-dimensional graphic data thereto for display, control and/or for processing purposes. A wide variety of such devices, commonly known as "digitizers", have been proposed and used for such purposes. Additionally, it is well known that printed overlays, or menus, placed on a digitizer tablet provide a fast and convenient method and means for permitting operator selection therefrom of drawing tools, fonts, and other computer executable functions printed thereon. Additionally, overlays placed on a digitizer tablet provide an advantage over conventional means of "point-and-click" monitor selection of menu items in that a larger number of simultaneously viewable items can be presented on a digitizer tablet. Printed overlays also enable the computer monitor work area to be devoted entirely to the display of working documents with little or no area thereof devoted to point-and-click menu items. A typical form of digitizer is shown in U.S. Pat. No. 3,684,828 to Maher. The digitizer normally includes a relatively flat surface for supporting one or more overlays in the form of a map, drawing or other source of graphic data, a stylus or other pointing device or cursor for designating individual points on the surface of each of such overlays, and means defining an X-Y, or rectangular, coordinate system for determining the rectangular coordinates for each individually designated point on each of such overlays. Well known interface circuitry is provided for converting the thus derived rectangular coordinate data into digital numbers arranged in an appropriate communication format for transmission to a computer for further processing. The Maher patent utilizes a piezoelectric substrate to detect the coordinates of the designated points by measuring the surface wave pulses propagating through the substrate surface. U.S. Pat. No. 3,692,936 to Moffitt discloses an acoustic digitizer, whereas, U.S. Pat. No. 4,177,354 discloses a digitizer employing a light responsive layer and a grid system which is used in combination with a light spot emitting stylus to generate digital coordinate signals. The digitizer of U.S. Pat. No. 4,255,617 to Caru et al employs a cursor with a capacitive pickup in combination with a platen comprising a flat surface within which are embedded two orthogonal grids, each consisting of uniformly spaced individual conductors. U.S. Pat. No. 4,318,096 to Thornburg et al discloses a rectangular coordinate tablet which is used in combination with an electrically conductive pen and an analog-to-digital converter to provide rectangular coordinate data to a computer. The tablet employs a piezoelectric audio pickup which produces a succession of pulses when the stylus is drawn across a textured surface such as a sheet of paper. Such orthogonally arranged sensors enable the direction of motion on a surface to be determined and "digitized" in each access by a bidirectional pulse counter.
In each of the systems referred to above, it is essential that the physical orientation of the overlay relative to the digitizer tablet surface, together with the particular scale and position of the overlay on the tablet surface, must be such that the position of the stylus on the overlay corresponds to the point on the tablet that will generate the correct coordinate signals for addressing the correct file stored in the computer memory. Misalignment results in the system becoming inoperative for the intended purpose.
In U.S. Pat. No. 5,010,323 issued to C. J. Hoffman, the same inventor as that of the present application, and which disclosure is incorporated herein by reference, there is disclosed a system wherein the utilized overlay may be physically positioned on the surface of the digitizer tablet in any physical orientation with respect to the coordinate axes of the digitizer tablet surface and, additionally, the overlay may be of any desired size. In the system disclosed in said '323 Hoffman patent, the physical orientation of the overlay on the digitizer tablet surface is automatically "transformed" to coincide with the coordinate axes of the digitizer tablet surface. Additionally, the overlay is provided with appropriate scaling information for automatically normalizing the size and position of the overlay.
An historical disadvantage of selecting menu items from overlays by each of the foregoing systems, when compared with point-and-click menu selection from the monitor screen by means of a cursor-position generating stylus in the form of a mouse or pen, or a self contained cursor-position generating stylus (e.g. "tailless mouse"), or the like, is that it has been necessary in each of such prior art systems that the vision of the computer operator be shifted from the monitor screen to the surface of the tablet, and back again, each time an overlay menu item is selected. This constant back and forth shifting of the line of vision of the operator is reported to be a significant cause of operator fatigue. However, in accordance with applicant's invention, there is provided an interactive overlay-driven computer display system which obviates the need for any back and forth shifting of operator vision between the monitor screen and the surface of the tablet, as in prior systems. Greater use of peripheral vision is possible, with reduced need for the constant refocusing of the eyes of the operator. Implementation of the present invention enables digitizer tablets with an appropriately designed stylus to perform as well as a mouse (with or without a tail) in all aspects of technical performance and human factors of touch and feel.